Flowable compositions containing cocoa butter display a relatively complicated behaviour which is to be attributed to the fact that in a very narrow temperature range between about 30.degree. and about 40.degree. C., the cocoa butter can assume and pass through very different states of crystallisation; both the properties of the flowable composition, especially its viscosity, and the properties of the chocolate or chocolate coatings produced therefrom by cooling and setting are very greatly dependent upon the state of crystallisation present in each case. Although the processes have not yet been clarified in detail, nevertheless, on the basis of experience and the theoretical concepts available hitherto it has been possible to develop specific methods of treatment of compositions containing cocoa butter, in which it is possible to combine good processibility of the composition with favourable properties of the solidified chocolate produced therefrom, especially as regards gloss and stability against the formation of fat bloom. These preparation processes in the case of chocolate are known in the art under the name "tempering" or "pre-crystallisation". By a well-tempered chocolate composition there is to be understood relatively thin liquid composition which on cooling forms a high-gloss surface which does not tend to the formation of fat bloom in storage.
Special difficulties arise if a flow of cocoa butter-containing composition after tempering or pre-crystallisation is not caused to solidify as a whole, as is the case for example in the production of block chocolate, but only a fraction is consumed in one cycle and the remainder undergoes further cycles. In this case the quantity consumed in each cycle can be made up by the supply of a corresponding additional quantity. This process is encountered predominantly in so-called coating machines, in which any articles, for example pieces for confectionary, are coated with the composition. In this case the procedure is generally adopted whereby a many times too large flow of the composition is poured over the articles and the major part of the proportion which runs away unused is returned in the cycle for renewed use. In such applications the composition must be kept over considerable periods of time as far as possible without change in the state of crystallisation which is most favourable for working. In order to achieve the highest possible uniformity of the coatings, it is sought to keep the viscosity practically constant as far as possible over the entire working period (normally one day). In most cases the thinnest possible coatings and correspondingly low viscosities are desired, and frequently for the purpose of adjustment and regulation of the thickness of the coatings a regulatable blower is also provided. With the ordinary methods of tempering or pre-crystallisation, the viscosity cannot be kept constant over the relatively long periods of time in the desired manner; instead one observes an irreversible increase of the viscosity despite the temperature being kept constant, and it is very difficult to obtain a constantly thin coating layer by other means, for example by increasing the output of the said blower. Moreover once the composition has become thicker more unfavourable properties appear after cooling; more especially the gloss of the produced coatings deteriorates. Therefore, frequently in practice the whole composition is tempered in the cycle afresh at relatively short time intervals or even at every circulation, as a whole or at least a considerable part. Since the tempering operation itself is also quite complicated a considerable expense for procedure and apparatus is incurred.
Methods for pre-crystallisation (tempering) are also known in which it is possible to obtain compositions the viscosity of which remains constant over lengthy periods of time (if the temperature is kept constant accordingly), so that these compositions can be stored without re-tempering over lengthy periods of time. According to present day knowledge this is based on the fact that, in these methods, cocoa butter crystals are obtained in the stable, so-called .beta.-modification, while in the methods known earlier which were based predominantly upon the principle of seeding with solid chocolate, predominantly crystals of the unstable so-called .beta.'-modification were formed. It has appeared that with the use of the described compositions of constant viscosity a considerably longer and more trouble-free operation is possible even of coating apparatuses. Since however in such and other apparatuses where the composition is conducted in the cycle and used repeatedly, greatly varied influences act upon the composition, for example acceleration, retardation, reversal, contact with various materials, especially the articles to be coated, contact with air, division of the surface, etc. Even if compositions practically of constant viscosity per se are used, troubles can arise the causes of which are mostly complex and the elimination of which is accordingly difficult. However, even in the case of compositions which are tempered in accordance with older methods and accordingly have a viscosity which per se is not constant, due to the described and possibly also other influences in the cycle conducted, there is a considerable number of sources of potential troubles, so that even with these compositions, additional difficulties and variations of the viscosity can occur, the cause of which is difficult to perceive.